This invention relates to a passive optical position detecting and measuring system.
Generally speaking, the concept of measuring the position of an object using optical means is known. For example:
(1) Hamamatsu Systems, Inc. of Waltham, Mass. manufactures a system which measures the position of multiple points using light emitting diodes and a position sensing detector (PSD). The LED's are attached to the object whose position is to be determined and are illuminated in sequence. The position sensing detector observes the LED signals and determines the object's position in two dimensions. If three dimensional determinations are desired, two PSD's are used.
(2) Hewlett-Packard Company manufactures a coordinate determination system which uses two digital theodolites as angle measurement instruments. A computer translates data received therefrom into x, y and z coordinates. Telescope cross-hairs are used to visibly identify the target spot. An aiming point is defined by one of three methods: (1) placement of a stick-on optical tooling target on the object; (2) sighting of a feature such as a rivet, corner, etc. on the object; (3) use of a highly collimated low power laser aimed at the object.
(3) A paper entitled "Electronic Device Using the Retro-Reflective Concept" by Hodgetts, et al. discloses a system utilizing an infrared light source, a retro-reflector mounted on the user's eyeglasses and a sensor device to determine the position of the reflected light. LED's surround the sensor and illuminate the area of the user's head. The system can only measure the relative position change (in two dimensions) of one point and, consequently, an active target board is necessary.
Several U.S. Patents disclose subject matter generally relevant to the instant invention:
(1) No. 2,133,241 to Baker measures the distance to an object. The system uses two light sources placed on opposite sides of a photocell which has a lens placed in front of it. The light sources are moved by a drive system to line up the light reflected from the object with the lens. The system is designed for long distance range such as distances used in an altimeter system, and is different from the instant invention in that (a) it only measures distance, not coordinates; (b) only one sensor is used; (c) the light sources are moved to determine the distance; (d) at short distances, the system would have poor resolution and accuracy.
(2) No. 3,002,419 to Vyce discloses an optical system for detection of translation of an object from a desired spatial position. In one embodiment, motors are used to align two detectors relative to a light source to receive the desired signals. The device equates detector movement to object position. The object has mounted thereon two reflectors, one a roof reflector sensitive only to changes in the angle of incidence of the light along a horizontal axis and the other a retro-reflector which operates in a manner well known.
The system used two different wavelengths of light as each detector is sensitive to only one of these wavelengths. The system is different from the instant invention in that (a) the detectors are moved to determine location; (b) two reflectors are used with separate measurements made with each; (c) position per se is not measured, rather only relative translation from a pre-determined position is determined; (d) only one target may be scrutinized.
(3) No. 3,202,040 to Burkhart discloses a system which uses reflectors attached to spaced buoys to allow a determination to be made of the position of a submarine with respect to the buoys. This system differs from the instant invention in that (a) the detector moves and the targets are stationary; (b) the system requires more than one target mirror to operate; (c) the position of the targets is pre-determined; and (d) only distance to the target is measured.
(4) No. 4,007,383 to Wessner is a device disclosed as capable of detecting the position of two objects relative to one another. The following differences from the instant invention are representative: (a) there is a significant separation between the light source and the sensor; (b) the device utilizes only one wavelength to sense location; (c) the device only measures relative angle to the target in one plane.
(5) No. 4,341,447 to Biber discloses a system wherein the distance from a camera to objects to be photographed is determined. Biber is different from the instant disclosure in that (a) the objects incude LED light sources which move therewith; (b) distance not location is measured; (c) only one wavelength of light is used; (d) only the relative angle in one plane is measured.
Further examples of U.S. Patents including subject matter generally relevant to the teachings of instant invention but less relevant than the above discussed patents are: U.S. Pat. Nos. 3,759,614, 3,773,422, 3,885,872, 4,076,383, 4,105,925, 4,207,002, 4,303,335, 4,304,487, 4,309,618, 4,313,654, 4,320,462 and 4,330,202.